Control device for controlling rigidity and deformation of car body

ABSTRACT

A control device for controlling rigidity of a car body has device for adjusting rigidity of a right side frame and a left side frame extending in the longitudinal direction of a car. The device is attached to the side frames. The control device has a controller for controlling operation of the device for adjusting rigidity of the right and left side frames according to a form of collision judged by an output of a collision detector such as an acceleration sensor. Further, a control device for controlling deformation of a frame has an actuator for generating a force in a direction of restricting or facilitating deformation of a frame, an external force detection sensor for detecting an external force inputted into the frame, and a controller for controlling operation of the actuator according to an output signal of the external force detection sensor. The actuator is arranged in a portion of the frame in which deformation of the frame greater than that of the periphery is predicted. Due to the foregoing, rigidity of the right and left side frames can be adjusted to a value appropriate for a form of collision by the device for adjusting rigidity of a right and a left side frame. Accordingly, it is possible to absorb an impact of collision appropriately in any form of collision including overall collision and partial collision.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control device for controllingrigidity of a car body or deformation of a frame of a car body. Anappropriate level of rigidity can be provided by the control deviceaccording to a form of collision of the car having a structure ofabsorbing an impact generated by collision.

The present application is based on Japanese Patent Applications No.Hei. 10-91552 and No. Hei. 10-206156, which are incorporated herein byreference.

2. Description of the Related Art

Since rigidity of a car body has an important effect upon safety ofdriving of the car, various countermeasures are taken for enhancingrigidity of the car. For example, frame members composing the car bodyare composed of steel plates of high strength, thickness of the framemembers is increased, and reinforcement members are attached toappropriate portions of the frame members. At the same time, from theviewpoint of protecting passengers in the case of collision, it isdesirable to provide a body structure capable of appropriately absorbingenergy generated in collision. This absorption of impact energygenerated in collision is mainly conducted by plastic deformation of aright and a left side frame extending in the longitudinal direction atthe front portion of the car body. When rigidity of the side frames isappropriately set, deceleration generated in a passenger's chamber inthe case of collision can be reduced, and the passenger is given animpact, the intensity of which is reduced.

In the case of a form of collision such as a front barrier collision inwhich the front surface of a car body collides entirely (this form ofcollision will be referred to as an overall collision in thisspecification hereinafter), an external force given to the car incollision is dispersed to the right and the left side frame. On theother hand, in the case of a form of collision such as an offsetcollision in which the front surface of a car body partially collides(this form of collision will be referred to as a partial collision inthis specification hereinafter), an external force given to the car incollision is concentrated upon one of the side frames. For the abovereasons, the following problems may be encountered. For example, whenrigidity appropriate for partial collision is set in each side frame,the rigidity becomes too high when an impact of collision is absorbed inthe case of an overall collision, and a high deceleration is generated.On the other hand, when rigidity appropriate for overall collision isset in each side frame, the rigidity becomes insufficient in the case ofa partial collision, and an impact can not be sufficiently absorbed andthe passenger's chamber is greatly affected by the collision. Asdescribed above, it is difficult to compose the side frames so that themost appropriate impact absorption can be conducted by them in bothforms of collision.

Further, physical strength such as rigidity or breaking characteristicis affected by a stress-strain characteristic of material itself.Further, physical strength is affected by a sectional form representedby moment of inertia of area, and a shape in the longitudinal directionof a frame represented by a neutral axis of the frame. Furthermore,deformation of the frame is changed by an intensity and direction of anexternal force inputted into the frame, and a mechanical strength of theframe is greatly changed by a state of deformation. For example, whenthe frame is given an external force of a direction in which bendingmoment is generated in the frame, in many cases, the bending strength isinsufficient compared with the compression strength. Therefore, bucklingis caused in the frame. Accordingly, the mechanical strength is greatlyinsufficient compared with a case in which the frame is given anexternal force in the axial direction.

Consequently, in order to obtain predetermined rigidity and breakingcharacteristic, it is necessary to consider a state of deformation ofthe frame according to an intensity and direction of a predictedexternal force when a shape of the frame is designed. It is possible tooptimize the shape of the frame by conducting a prediction in simulationor making experiments. However, from the actual viewpoint, it is verydifficult to realize the most appropriate shape and state of deformationof the frame, because the manufacturing cost, space and weight arerestricted.

SUMMARY OF THE INVENTION

The present invention has been accomplished to solve the above problemsof the conventional art. It is an object of the present invention toprovide a control device for controlling rigidity of a car body by whichan appropriate impact absorption can be conducted irrespective of a formof collision.

It is another object of the invention to provide a control device forcontrolling deformation of a frame capable of obtaining a predeterminedstrength characteristic by controlling a state of deformation of theframe without relying on the shape.

In order to accomplish the above objects, the present invention providesa control device for controlling rigidity of a car body comprising: ameans 4 for adjusting rigidity of a right and a left side frame 2, 3extending in the longitudinal direction of the car 1, the means beingattached to the side frames 2, 3; and a control means 8 for controllingoperation of the means for adjusting rigidity of a right and a left sideframe according to a form of collision judged by an output of acollision detection means 5. Due to the foregoing, rigidity of the rightand the left side frame can be adjusted to values appropriate for theform of collision by the means for adjusting rigidity of the right andthe left side frame. Accordingly, it is possible to absorb an impact ofcollision appropriately in any form of collision including overallcollision and partial collision.

The means for adjusting rigidity of the side frame is a solid elementactuator such as a piezoelectric element or a magentostriction elementto generate a force in a direction of restricting plastic deformation ofthe side frame or facilitating plastic deformation of the side frame.Alternatively, the means for adjusting rigidity of the side frame is areinforcement member capable of being displaced between a position atwhich rigidity of the side frame is enhanced and a position at which noinfluence is given to rigidity of the side frame. Further, it ispossible to provide the same action by using a reinforcement membercombined with the side frame via explosion bolts which are brokenaccording to an operation signal sent from the control means.

In this connection, examples of the collision detection means are: anacceleration sensor for detecting acceleration generated in thelongitudinal direction of a car body in collision; a strain sensor fordetecting strain generated in the side frame in collision; and adisplacement sensor for detecting displacement of a measurement pointwhich is caused by deformation of the car body in collision, wherein themeasurement point is appropriately set in the side frame or bumperattaching member. Concerning the acceleration sensor, it is possible touse a piezoelectric element from which a voltage signal is outputtedaccording to strain, a semiconductor, the resistance of which is changedby strain, and glass fibers, the transmission characteristic of which ischanged by strain, and acceleration can be detected by strain caused ina support section of the sensor. Concerning the strain sensor, thesensors described in the above acceleration sensor can be used. Inaddition to that, it is possible to use a solid element actuatorcomposed of a piezoelectric element or a magentostriction element.Concerning the displacement sensor, it is possible to use a variableresistor, a laser beam displacement meter, and a limit switch, thestructure of which is a simple gap type.

Further, in order to accomplish the above objects, the present inventionprovides a control device for controlling deformation of a framecomprising: an actuator 2 for generating a force in a direction ofrestricting or facilitating deformation of a frame 1; an external forcedetection sensor 3 for detecting an external force inputted into theframe; and a controller 4 for controlling operation of the actuatoraccording to an output signal of the external force detection sensor,wherein the actuator is arranged in a portion 6 of the frame in whichdeformation of the frame greater than that in the periphery ispredicted, so that deformation of the frame is suppressed or a shape ofthe frame is induced to a predetermined shape according to the externalforce obtained from the output of the external force detection sensor.

Due to the foregoing, it is possible to control a state of deformationof the frame by suppressing deformation of the frame member and inducingthe frame member into a predetermined shape when the actuator isoperated according to an intensity and direction of an external forcegiven to the frame. Therefore, it is possible to arbitrarily changevarious strength characteristics of the frame such as a breakingcharacteristic and vibration characteristic which are determined by theshape of the frame.

The aforementioned portion of the frame member, in which deformationgreater than that of the periphery is predicted, is defined as a portionin which the mechanical strength is lower than that of the peripherybecause of a restriction of space and weight. Further, theaforementioned portion of the frame member, in which deformation greaterthan that of the periphery is predicted, is defined as a portion, themechanical strength of which is the same as that of the periphery,however, stress of deformation is concentrated upon the portion due tothe shape of the cross-section of the frame, a state of the neutral axisand an arrangement of the reinforcement member, so that deformationgreater than that of the periphery is caused in the portion. Thisportion may be necessarily or intentionally formed in the frame.

When an actuator is arranged at a position corresponding to the aboveportion in which the occurrence of great deformation is predicted, itbecomes possible to effectively control the strength characteristic ofthe frame. When an amount of deformation of the frame with respect to aforce generated by the actuator is increased in this portion, themechanical strength of which is low, it is possible to realize controlof deformation of the frame by an actuator of a relatively smallcapacity. Actually, the portion of great deformation in which theactuator is arranged is specified, and the arrangement of the actuatorand the method of control conducted by the controller are determined bymaking experiments and simulation in which various conditions such as anintensity and direction of a predicted external force are considered.

Concerning the actuator for conducting deformation control in an elasticdeformation region of the frame in accordance with a relatively lowintensity of external force given to the frame such as a vibrationforce, it is necessary to provide a characteristic in which the actuatoris restored to the initial state when the external force is removed. Inorder to provide such a restoring property to the actuator, it ispreferable to use a magentostriction element in which a force isgenerated according to an intensity of the magnetic field. It is alsopossible to use a piezoelectric element in which a force is generatedaccording to voltage impressed upon the piezoelectric element.

On the other hand, the actuator to be operated in a plastic deformationregion of the frame may be an actuator capable of outputting a forcecorresponding to a predicted external force, that is, it is unnecessaryto provide the aforementioned restoring property. Such an actuator maybe composed of a magentostriction element, however, the actuator may becomposed of a member made of shape-memory alloy, which is previouslydeformed by compression, and an electrically heating body for heatingthe member made of shape-memory alloy according to a control signal sentfrom the controller. Due to the foregoing, it is possible to obtain aforce for restricting and facilitating deformation of the frame by arestoring force of the member of shape-memory alloy heated by theheating body.

An example of the aforementioned external force detection sensor is astrain sensor for detecting strain generated in the frame itself orother members connected to the frame. In order to detect an externalforce of collision, it is preferable to provide an acceleration sensorfor detecting acceleration generated in a car body in collision. Whenthe acceleration sensor is used, it is possible to detect an input ofthe external force earlier than a strain sensor, and predetermineddeformation control can be started immediately. Further, it is possibleto adopt a displacement sensor for detecting displacement of ameasurement point located at an appropriate position when a member isdeformed. In this connection, concerning the detection of a direction ofthe external force, even if an external force detection sensor capableof detecting an external force in a single direction is used, it ispossible to detect the direction of the external force when a pluralityof the sensors are arranged and intensities of external forces detectedby the sensors are compared with each other.

Features and advantages of the invention will be evident from thefollowing detailed description of the preferred embodiments described inconjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is an upper surface view showing a state in which a controldevice for controlling rigidity of a car body of the present inventionis applied to a car body frame;

FIG. 2 is a perspective view showing a primary portion of a side frameinto which the piezoelectric actuator shown in FIG. 1 is incorporated;

FIG. 3 is a perspective view showing the piezoelectric actuator shown inFIG. 1;

FIG. 4 is a block diagram showing the control device for controllingrigidity of a car body shown in FIG. 1;

FIG. 5 is a flow chart showing a control method of the control devicefor controlling rigidity of a car body shown in FIG. 1;

FIG. 6 is a perspective view showing a primary portion of a controldevice for controlling rigidity of a car body in which amagentostriction actuator is used;

FIG. 7 is a longitudinal cross-sectional view showing a primary portionof a control device for controlling rigidity of a car body in which areinforcement plate is used;

FIG. 8 is a longitudinal cross-sectional view showing a variation of thecontrol device for controlling rigidity of a car body shown in FIG. 7;

FIG. 9 is a longitudinal cross-sectional view showing another variationof the control device for controlling rigidity of a car body shown inFIG. 7;

FIG. 10 is a longitudinal cross-sectional view showing still anothervariation of the control device for controlling rigidity of a car bodyshown in FIG. 7;

FIG. 11 is a graph showing a change with time of acceleration generatedin a car body in collision;

FIG. 12 is a block diagram showing an example in which a solid elementactuator is also used as a collision detection means;

FIG. 13 is a perspective view showing an embodiment of the controldevice for controlling deformation of a frame of the present invention;

FIG. 14 is a front view showing an actuator made of shape-memory alloy;

FIG. 15 is an upper surface view of a frame shown in FIG. 13;

FIG. 16 is an upper surface view, which is drawn in the same manner asthat of FIG. 15, showing another state of attaching an actuator made ofshape-memory alloy;

FIG. 17 is a cross-sectional view showing another state of attaching anactuator made of shape-memory alloy.

FIG. 18 is a cross-sectional view showing another state of attaching anactuator made of shape-memory alloy;

FIG. 19 is a front view showing a magentostriction element actuator;

FIG. 20 is a front view, which is drawn in the same manner as that ofFIG. 19, showing another state of a magentostriction element actuator;

FIG. 21 is a perspective view showing another embodiment of the controldevice for controlling deformation of a frame of the present invention;and

FIG. 22 is a graph showing a result of a compression test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the appended drawings, the structure of the presentinvention will be explained in detail.

FIG. 1 is a view showing a control device for controlling rigidity of acar body of the present invention. This control device for controllingrigidity of a car body includes: a plurality of piezoelectric actuators4, which are a frame rigidity adjustment means, attached to the rightand the left side frame 2, 3 which extend in the longitudinal directionof a car body 1; a pair of acceleration sensors 5, which are an impactdetection means, attached to the right and the left side frame 2, 3; anda controller 8, which is a control means, arranged on a center frame 7.Rigidity of the side frames 2, 3 is relatively low so that it can meet arequirement in the case of overall collision.

As shown in FIG. 2, the piezoelectric actuators 4 are arranged beinginterposed between the end portion attaching members 11, 12 and theintermediate portion attaching member 13, wherein the end portionattaching members 11, 12 and the intermediate portion attaching member13 are tightly fixed onto outer wall surfaces of the side frames 2, 3 inthe portions inside the neutral surface of two curved sections 9, 10 inthe crank-shaped curved sections of the side frames 2, 3. Under theabove condition, pairs of piezoelectric actuators are arranged inseries. The pairs of piezoelectric actuators 4 are arranged being bentalong the axial line of the side frame 2, 3 while the intermediateattaching sections 13 are interposed between the pairs of piezoelectricactuators 4.

As the detail is shown in FIG. 3, the piezoelectric actuator 4 includes:a rectangular plate-shaped piezoelectric element panel 15 composed ofPZT which generates a force according to voltage impressed by thecontroller 8; a pair of copper electrodes arranged on both sides of thepiezoelectric element panel 15; and a cover body 18 made of epoxy resinwhich covers the piezoelectric element panel 15 and copper electrode 16,wherein the cover body 18 is integrated with the piezoelectric elementpanel 15 and copper electrode 16 by means of thermo-compression bonding.In this connection, a conductive sheet containing Ni may be providedbetween the piezoelectric element panel 15 and the copper electrode 16,and both sides of the cover body 18 may be covered with a film ofpolyimide.

As shown in FIG. 4, the controller 8 includes: a pair of A/D converters21 for conducting A/D conversion on the output signals of the right andthe left acceleration sensor 5; CPU 22 for judging a form of collisionaccording to the output signals of A/D converters 21 and also foroutputting operation signals to predetermined piezoelectric actuators 4according to the result of judgment; and a switching circuit 24 forimpressing voltage of a power source 23 upon the piezoelectric actuators4 by the switching motion of transistors according to the output signalsof CPU 22.

In the control device for controlling rigidity of a car body composed asdescribed above, output signals of the right and the left accelerationsensor 5 are always inputted into CPU 22 via A/D converter 21.Therefore, as shown in FIG. 5, acceleration signals G_(L), G_(R), whichare output signals of the acceleration sensors 5, are compared withreference value G_(D) previously stored in a memory section (not shown)in the controller 8 (steps 1 to 3). In this case, when bothaccelerations G_(L), G_(R) are not lower than reference value G_(D), itis judged that the collision is an overall collision (step 4). In thiscase, the program is completed without operating the piezoelectricactuator 4. And both side frames 2, 3, the rigidity of which is set at arelatively low value so that the side frames 2, 3 can meet therequirement of an overall collision, are plastically deformed and animpact of collision is absorbed.

When both accelerations G_(L), G_(R) are lower than reference valueG_(D), it is judged that no collision has occurred (step 5). Therefore,the program is completed without operating the piezoelectric actuator 4in the same manner as that described above.

On the other hand, when left acceleration G_(L) is not lower thanreference G_(D) and right acceleration G_(R) is lower than referenceG_(D), it is judged that the collision is a partial collision on theleft (step 6). Therefore, voltage is supplied to the piezoelectricactuator 4, which is arranged in the left side frame 2, from a powersource (step 7). When left acceleration G_(L) is lower than referenceG_(D) and right acceleration G_(R) is not lower than reference G_(D), itis judged that the collision is a partial collision on the right (step8). Therefore, voltage is supplied to the piezoelectric actuator 4,which is arranged in the right side frame 3, from the power source (step9).

When voltage is impressed from the power source upon the piezoelectricactuator 4 arranged in either of the right 2 or the left side frame 3,an extending force is generated in the piezoelectric actuator 4 as shownby an arrow in FIG. 2. Due to the thus generated extending force, whenan external collision force is inputted into the side frame 2, 3 in theaxial direction as shown by arrow A in FIG. 2, a compressive deformationcaused in a portion where the piezoelectric actuator 4 is arranged isrestricted, so that rigidity of the side frame 2, 3 can be enhanced.Accordingly, the predetermined side frame 2, 3 can be put into arelatively high rigidity condition that is suitable for partialcollision. In this way, the impact of collision can be appropriatelyabsorbed.

In this case, the piezoelectric actuator 4 is operated in a direction sothat rigidity of the side frame 2, 3 can be enhanced. However, it ispossible to adopt an arrangement in which the piezoelectric actuator 4is operated in a direction so that rigidity of the side frame 2, 3 canbe reduced on the contrary. In this case, there are previously providedside frames 2, 3, the rigidity of which is relatively high so that theside frames 2, 3 can be suitably applied to partial collision, and onlywhen it is judged that the collision is an overall collision (step 4 inFIG. 5), the piezoelectric actuators 4 of both side frames 2, 3 aresimultaneously operated, and rigidity of both side frames 2, 3 isreduced to a value suitable for overall collision.

FIG. 6 is a view showing an example in which a magentostriction actuator31 is arranged in a straight line portion of the side frame 2, 3 so thatit can be used as a frame rigidity adjustment means.

The magentostriction actuator 31 include: a magentostriction elementpanel 32 for generating a force according to an intensity of a magneticfield; an exciting coil 33 for generating a magnetic field to beimpressed upon the magentostriction element panel 32; and a yoke 34which is a magneto-induction means for inducing a magnetic fieldgenerated by the exciting coil 33 onto the magentostriction elementpanel 32. The magentostriction element panel 32 is a rectangularplate-shaped panel made of giant-magentostriction material such as alloyof Tb—Dy—Fe by a conventional forming method such as casting, cutting,sintering or vapor-deposition. The yoke 34 is made of soft magneticmaterial such as electromagnetic steel. The yoke 34 includes: a pair ofmagnetic poles 35, 36 respectively joined to a pair of side edgeportions, which are opposed to each other, of the rectangularmagentostriction element panel 32; a pair of arms 37, 38 which areextended from centers of both magnetic poles 35, 36 in the samedirection; and an iron core 39 arranged between both arms 37, 38,wherein the exciting coil 33 is attached onto an outer circumference ofthe iron core 39. In this connection, surfaces of the magnetic poles 35,36 coming into contact with the side frame 2, 3 may be covered with amagnetic sealing layer made of nonmagnetic material such as Mo or Al.

In this structure, the magentostriction actuator 31 is incorporated intoa rectangular attaching hole 40 formed on a peripheral wall of the sideframe 2, 3, and an operation current is supplied to the exciting coil 33from the controller 8 via a lead wire 41 inserted into the side frame 2,3.

On the peripheral wall of the side frame 2, 3, there is provided astrain sensor 42 composed of a piezoelectric element which is acollision detection means. A strain signal of the strain sensor 42 isinputted into the controller 8 at all times, and a form of collision isjudged by the controller 8 according to this strain signal in the samemanner as that described before.

According to the result of judgment of the form of collision, a controlvoltage is impressed upon the exciting coil 33 by the controller 8.Then, a force in a direction of suppressing strain of the peripheralwall of the side frame 2, 3 is generated on the magentostriction elementpanel 32. This force is transmitted to the side frame 2, 3 via themagnetic poles 35, 36 of the yoke 34. This force generated on themagentostriction element panel 32 suppresses deformation of a straightline section of the side frame 2, 3, so that a buckling stress of thestraight line section of the side frame 2, 3 can be increased. In thisway, it is possible to obtain a predetermined value of rigidity.

In this connection, the embodiment shown in FIG. 2 and the embodimentshown in FIG. 6 are different from each other in the viewpoints of themethods of attaching the piezoelectric actuator 4 and themagentostriction actuator 31 to the side frame 2, 3. Further, theembodiment shown in FIG. 2 and the embodiment shown in FIG. 6 aredifferent from each other in the viewpoints of the positions at whichthe piezoelectric actuator 4 and the magentostriction actuator 31 areattached. However, the piezoelectric actuator 4 and the magentostrictionactuator 31 have the same function. Therefore, it is possible to adoptan arrangement in which both actuators are arranged in the opposite way,and it is also possible to adopt an arrangement in which both actuatorsare combined with each other appropriately.

FIG. 7 is a view showing an example in which a reinforcement plate 51 isarranged inside a right and a left hollow side frame 2, 3. In thisstructure, one end of the reinforcement plate 51, which is arranged inthe substantially horizontal direction, is connected with a surfaceinside an inclined portion of the upper wall 52 of the side frame 2, 3,that is, the reinforcement plate 51 is attached in the manner ofcantilever. In the proximity of the other end of the reinforcement plate51, there is provided a protrusion 54 which is protruded from an innersurface of the lower wall 53 of the side frame 2, 3. On the upper andthe lower surface of the reinforcement plate 51, there are respectivelyprovided piezoelectric actuators 55, the structure of which issubstantially the same as that of the piezoelectric actuator 4 shown inFIG. 3. Rigidity of the right and the left side frame 2, 3 is relativelylow so that the side frames can meet the requirement of overallcollision.

When an external collision force in the direction of arrow A is inputtedinto the side frame 2, 3 in the case where the reinforcement plate 51 isset horizontally at the initial position, a forward end of thereinforcement plate 51 is caught by the protrusion 54. Therefore,deformation of the upper 53 and the lower wall 53 of the side frame 2, 3is regulated, so that rigidity of the side frame 2, 3 can be enhanced.

On the other hand, when an operation voltage is impressed upon the upperand the lower piezoelectric actuator 55, a contraction force isgenerated in the upper piezoelectric actuator 55, and an extending forceis generated in the lower piezoelectric actuator 55. Accordingly, thereinforcement plate 51 is bent as shown by a virtual line in thedrawing. When an external collision force is inputted into the sideframe 2, 3 under the above condition, it is impossible for the forwardend of the reinforcement plate 51 to engage with the protrusion 54, andthe reinforcement plate 51 does not function effectively. Accordingly,the side frame 2,3 is plastically deformed in a relatively low rigiditycondition.

In this case, unlike the control method in the embodiment shown in FIG.5, only when it is judged that both acceleration G_(L) and accelerationG_(R) are not lower than reference G_(D), that is, only when it isjudged that the collision is an overall collision (step 4 in FIG. 5),the piezoelectric actuators 55 arranged on the reinforcement plates 51of the right and the left side frame 2, 3 are simultaneously operated.Due to the foregoing, both side frames 2, 3 arranged on the right andleft are set in a relatively low rigidity condition so that an impact ofcollision can be absorbed. Therefore, it is possible to reducedeceleration generated in the passenger's chamber.

In other cases, the piezoelectric actuators 55 are not operated, and thereinforcement plate 51 is kept at the initial position. Due to theforegoing, in the case of partial collision on the right or the left,the reinforcement plate 51 functions, and a predetermined side frame 2,3 is plastically deformed in a relatively high rigidity condition.Therefore, an impact of collision can be appropriately absorbed.

In this connection, on the contrary to the above case, it is possible toadopt an arrangement in which the reinforcement plate does not functionat the initial position and the reinforcement plate is displaced by thepiezoelectric actuator 55 to a position at which the reinforcement platefunctions. In this case, the same control method as that shown in FIG. 5may be adopted. It is also possible to adopt an arrangement in which thepiezoelectric actuator 55 is operated in such a manner that it displacesthe reinforcement plate 51 and enhances rigidity of the reinforcementplate 51 itself. Further, it is possible to adopt an arrangement inwhich the same magentostriction actuator as the magentostrictionactuator 31 shown in FIG. 6 is used instead of the piezoelectricactuator 55 in order to displace the reinforcement plate 51.

FIGS. 8 to 10 are views showing variations of the embodiment illustratedin FIG. 7. In the arrangement shown in FIG. 8, there is provided areinforcement plate 61 at a bent section of the side frame 2, 3 in thesame manner as that described before. This reinforcement plate 61 isarranged in such a manner that one end of the reinforcement plate 61 istiltably fixed onto an upper wall 52 of the side frame 2, 3. By theaction of a motor 62, which is operated according to an operation signalof the controller 8, the reinforcement plate 61 is tilted upward anddisplaced to a position at which the reinforcement plate 61 does notfunction as shown by a virtual line in FIG. 8. In this connection, it ispossible to adopt an arrangement in which the reinforcement plate 61 istilted by a spring instead of the motor 62. In this case, a lock meansfor locking the spring may be released according to an operation signalsent from the controller 8.

In FIG. 9, in the same manner as that of the embodiment shown in FIG. 8,the reinforcement plate 63 is tiltably fixed to the side frame 2, 3.This reinforcement plate 63 is tilted by a magnetic attraction forcegenerated between a coil 64 arranged on the reinforcement plate 63 and astationary iron core 65 arranged in the side frame 2, 3. In FIG. 10,instead of the protrusion 54 in the embodiment shown in FIG. 7, there isprovided a step section 66, which engages with a forward end portion ofthe reinforcement plate 51, on a lower wall 53.

In this connection, in the embodiment shown in FIG. 1, a form ofcollision is judged by a difference of intensity between theacceleration detected by the right acceleration sensor 5 and thatdetected by the left acceleration sensor 5. However, it is possible tojudge a form of collision by one acceleration sensor arranged at thecenter of a car body, for example, by one acceleration sensor arrangedon the center frame 7. FIG. 11 is a graph showing changes inacceleration generated in a car body in the cases of an offset collisionand a head-on collision of an actual car. As can be seen on the graph,there is a great difference between the waveform of the change in theoffset collision and that of the change in the head-on collision. Thatis, a rise in the acceleration of the offset collision is slower than arise in the acceleration of the head-on collision. Therefore, a peak ofthe acceleration of the offset collision is shifted from a peak of theacceleration of the head-on collision. When a judgment reference is madeaccording to this difference, it is possible to discriminate a form ofcollision. When a form of collision is judged according to a peakgenerated in the proximity of 8 ms in the case of a head-on collision,it is possible to conduct judgment in its early stages. In thisconnection, the waveform of a change in acceleration shown in FIG. 11depends upon the structure of a car body. Accordingly, when the judgmentreference is actually made, it is made appropriately according to a carbody into which this apparatus is incorporated. In the case where a formof collision is judged by one acceleration sensor, it is possible toshare an acceleration sensor used for an air bag.

In the above embodiment, the acceleration sensor and the strain sensorare used for the collision detection means. However, since thepiezoelectric element itself composing a solid actuator has a functionof outputting voltage according to strain and the magentostrictionelement is capable of outputting a voltage signal via the exciting coilaccording to strain, it is possible to adopt an arrangement in which asolid element actuator 71 composed of the piezoelectric element or themagentostriction element is used for the collision detection means. Inthis case, a state of the solid element actuator 71 is monitored by themonitor circuit 72, and when strain is detected, the level of which isnot lower than a predetermined value, a form of collision is judged byCPU 22. Other points of structure is the same as those shown in FIG. 4.That is, according to the result of judgment of a form of collision, anoperation signal for operating the solid element actuator 71 isoutputted from CPU 22, and voltage of the power source 23 is impressedupon the predetermined solid element actuator 71 via the switchingcircuit 24.

FIG. 13 is a view showing an embodiment of a control device forcontrolling deformation of a frame to which the present invention isapplied. This control device for controlling deformation of a frameincludes: a plurality of actuators 102 made of shape-memory alloy whichare arranged on an outer surface of a square cylindrical frame 101; aplurality of strain sensors 103 for detecting an external force inputtedinto the frame 101; a controller 104 for outputting a control signalaccording to a signal sent from the strain sensor 103; and a power feedsection 105 for feeding a drive electric current to the actuators 102made of shape-memory alloy according to the control signal sent from thecontroller 104.

In the frame 101, there is provided a great deformation section 106, themechanical strength of which is lower than that of the peripheralportion, and this great deformation section 106 is formed in such amanner that a portion of the circumferential wall of the frame is cutout all over the circumference. Moment of inertia of area of this greatdeformation section 106 is lower than that of the peripheral portion.Accordingly, this great deformation section 106 is greatly deformed by arelatively low force in the axial direction and bending moment. Theactuators 102 made of shape-memory alloy are arranged over the greatdeformation section 106 and attached to a pair of attaching members 107which are tightly fixed onto outer wall surfaces on both sides of thegreat deformation section 106.

The strain sensor 103 is tightly fixed onto the outer wall surface ofthe frame 101. This strain sensor 103 is capable of detecting an amountof strain in one direction, for example, in the axial direction of theframe 101. When amounts of strain detected by a plurality of strainsensors 103 are compared with each other, it is possible to judge adirection of the external force given to the frame. In this connection,when a pair of strain sensors 103 are arranged on one surface of theframe 101, the direction of the external force can be only judgedtwo-dimensionally. However, when the strain sensors 103, the number ofwhich is not less than three, are arranged on a plurality of surfaces ofthe frame 101, the direction of the external force can be judgedthree-dimensionally.

As the detail is shown in FIG. 14, the actuator 102 made of shape-memoryalloy includes: a rod 111 made of shape-memory alloy such as Ti—Ni—Cu;and a heater 112 arranged outside the rod 111 made of shape-memoryalloy. The heater 112 includes: a heating coil 113, a thermocouple 114;and a covering body 115 made of ceramics which covers the heating coil113 and thermocouple 114. The rod 111 made of shape-memory alloy ispreviously given a compressive deformation in the axial direction. Whenthe rod 111 made of shape-memory alloy is heated by the heater to whichelectric current is fed from the power feeding section 105, an extendingforce in the axial direction can be generated.

As shown in FIG. 15, one pair of actuators 102 made of shape-memoryalloy are arranged on one surface of the frame 101, and another pair ofactuators 102 made of shape-memory alloy are arranged on the othersurface of the frame 101, and these two surfaces of the frame 101 areopposed to each other. These actuators 102 made of shape-memory alloycan be independently controlled. When all actuators 102 made ofshape-memory alloy are equally operated, it is possible to obtain anextending force in the axial direction of the frame 101. On the otherhand, when the actuators 102 made of shape-memory alloy are unequallyoperated, it is possible to obtain a bending moment in a predetermineddirection in addition to the extending force in the axial direction. Inthis connection, the number and positions of the actuators 102 made ofshape-memory alloy are not limited to the above specific arrangement,but they may be appropriately determined so that a predetermined forcein the axial direction and bending moment can be obtained according tothe direction of a predicted external force.

In order to suppress deformation of the frame 101 when an external forcein the axial direction of the frame 101 is given, all actuators 102 madeof shape-memory alloy may be equally operated so as to cope with stressgenerated in the frame 101 in the axial direction. On the other hand,with respect to an external force in a direction oblique to the axialline of the frame 101, in order to cope with a force in the axialdirection and bending moment generated in the frame 101, each actuator102 made of shape-memory alloy may be operated by a predetermined ratioin accordance with an intensity and direction of external force given tothe frame 101. When the actuators 102 made of shape-memory alloy areoperated by a predetermined ratio so that an output exceeding anexternal force and also exceeding a resistance force of deformation ofthe great deformation section 106 can be outputted, it is possible tobend the great deformation section 106 and induce the frame into anarbitrary deformation condition.

FIGS. 16 to 18 are views showing variations of the actuators 102 made ofshape-memory alloy. The actuator 121 made of shape-memory alloy shown inFIG. 16 is arranged between the attaching members 122 fixed onto theouter wall surface of the frame 101 in the same manner as that of theactuator 102 made of shape-memory alloy described before. However, thisactuator 121 made of shape-memory alloy is curved along an outer surfaceof the great deformation section 106. The actuator 121 made ofshape-memory alloy having the above curved shape can be restored into astraight shape when it is heated. At this time, the attaching sections122 arranged on both sides are spread by a force of the actuator 102made of shape-memory alloy, and the frame 101 is given a predeterminedextending force. In FIG. 17, there is provided a straight actuator 124made of shape-memory alloy between the attaching members 123 arranged inthe frame 101 in such a manner that the inside of the frame 101 can bepartitioned by the attaching members 123. In this structure, when thestraight actuator 124 made of shape-memory alloy is arranged at aposition which deviates from the central axis of the frame 101, it ispossible to obtain a predetermined bending moment. In FIG. 18, there areprovided a pair of actuators 125 made of shape-memory alloy which arecurved into an arc-shape, and both ends of the actuators 125 made ofshape-memory alloy are fixed to the attaching members 126 which arefixed onto the inner wall surface of the frame 101, wherein opposingsurfaces of the actuators 125 made of shape-memory alloy are made tocome into contact with each other at the center. In this case, the frame101 is given an extending force when a pair of actuators 125 made ofshape-memory alloy, the centers of which are restricted to each other,are extended and restored.

Examples in which the actuators made of shape-memory alloy are used areshown above. Instead of the above examples, it is possible to usemagentostriction element actuators 131, 132 as shown in FIGS. 19 and 20.The above actuator made of shape-memory alloy has no restoring property.Therefore, it is used only in a case in which plastic deformation isconducted by a relatively high intensity of external force. However, themagentostriction element actuator has a restoring property. Therefore,the magentostriction element actuator can be applied to a case in whichelastic deformation is conducted by a relatively low intensity ofexternal force such as an external force generated by vibration.

The magentostriction element actuator 131 shown in FIG. 19 is composedin such a manner that a magentostriction element rod 133 for generatinga force according to an intensity of a magnetic field and an excitingcoil 134 for impressing the magnetic field upon the magentostrictionelement rod 133 are coaxially arranged, wherein the exciting coil 134 isarranged on an outer circumference of the magentostriction element rod133. The magentostriction element rod 133 is made of commonultra-magentostriction material such as Tb—Dy—Fe. In themagentostriction element actuator 132 shown in FIG. 20, a magnetic fieldgenerated by the exciting coil 135 is induced to the magentostrictionelement rod 137 via the magnetic inducing member 136. The magneticinducing member 136 is made of soft magnetic material such aselectromagnetic steel. These magentostriction element actuators 131, 132are attached to the frame 101 via the attaching members 107 fixed onto asurface of the circumferential wall of the frame 101, or alternativelythese magentostriction element actuators 131, 132 are attached to theframe 101 in such a manner that the magnetic inducing member 136 is alsoused as the attaching member.

Both the magentostriction element actuators 131, 132 and the actuatorsmade of shape-memory alloy 102, 121, 124, 125 can be jointly used. Forexample, an example of the control method in which the actuator 102 madeof shape-memory alloy shown in FIG. 14 and the magentostriction elementactuator 131 shown in FIG. 19 are combined with each other is shown asfollows.

First, inner stress of the frame 101 is calculated by the controller 104according to an amount of strain of the frame detected by the strainsensor 103. When this inner stress exceeds a reference value (100 Mpa to200 Mpa), it is judged to be plastic deformation, and the actuator 102made of shape-memory alloy, which corresponds to plastic deformation, isoperated. In this case, it is possible to operate the magentostrictionelement actuator 131 at the same time. Due to the foregoing, thebreaking strength of the frame 101 can be enhanced.

on the other hand, in the different manner from that described above,the magentostriction element actuator 131 is operated at all times in apredetermined direction so that strain of the frame 101 can berestricted or facilitated according to an output of the strain sensor103, so that deformation of the frame 101 is suppressed and thevibration characteristic is changed. Due to the foregoing, it ispossible to enhance rigidity of the frame 101 and further vibration andnoise can be reduced.

FIG. 21 is a view showing another embodiment of the control device forcontrolling deformation of a frame of the present invention. In thisstructure, there are provided a plurality of actuators 142 made ofshape-memory alloy on a square cylindrical frame 141 which is entirelycurved. In this case, pairs of actuators 142 made of shape-memory alloyare arranged in series. Each actuator 142 made of shape-memory alloygenerates an extending force by a restoring stress in the same manner asthat of the aforementioned actuator 102 made of shape-memory alloy. Thisactuator 142 made of shape-memory alloy is interposed between theattaching sections 143 which are tightly fixed onto an outer wallsurface of the inside of the bent frame 141. In the same manner as thatof the aforementioned embodiment, the control device for controllingdeformation of a frame of this embodiment further includes: a pluralityof strain sensors 103 for detecting an external force inputted into theframe 101; a controller 104 for outputting a control signal according toa signal sent from the strain sensor 103; and a power feed section 105for feeding a drive electric current to the actuators 142 made ofshape-memory alloy according to the control signal sent from thecontroller 104.

As shown by an arrow in FIG. 21, when a compressive force is given tothe frame 141, stress in the axial direction and bending moment aregenerated in the frame 141. Buckling generated by this bending momentgreatly affects a mechanical strength of the frame 141. On the otherhand, when bending moment, which copes with bending moment generated byan external force, acts on the frame 141 by the extending force of theactuator 142 made of shape-memory, and buckling of the frame 141 can beprevented.

In this embodiment, the entire curved frame 141 corresponds to a portionin which a great deformation is predicted in the present invention. Onthe other hand, in the embodiment (shown in FIG. 13) described before,the great deformation section 106 corresponds to a portion in which agreat deformation is predicted. However, it should be noted that thepresent invention is not limited to the above specific embodiments, butit is possible to adopt various embodiments. For example, it is possibleto adopt an embodiment in which a portion of the frame is thinner thanthe peripheral portion so that the mechanical strength of the portion islower than that of the peripheral portion. Since a great deformation iscaused in a portion close to a reinforcement member such as a bulkheadfor restricting deformation of the frame and also a great deformation iscaused in a portion upon which deformation stress is concentratedaccording to a form of the neutral axis of the curved frame. Therefore,these portions are suitable for controlling deformation.

The frame 141 of the embodiment (shown in FIG. 21) to which the presentinvention is applied was actually manufactured, and a compressivestrength test was made. The result of the strength test is shown in FIG.22. According to the result of the test, the following were found. Whenno control was conducted, that is, when no deformation control wasconducted by the actuator 142 made of shape-memory alloy, an amount ofabsorbed energy was not increased any more at a point where an amount ofcompression exceeded 100 mm, and buckling was caused at point A in FIG.22. On the other hand, when control was conducted, no buckling wascaused, and an amount of absorbed energy was continuously increased.This is substantially the same as a straight frame of the samecross-section. Therefore, it was found that the deformation controlcapacity was sufficiently high.

As described above, according to the present invention, rigidity of theright and the left side frame is adjusted to a value appropriate for aform of collision by the rigidity adjustment means of the right and theleft side frame. Therefore, an impact of collision can be appropriatelyabsorbed in any form of collision of head-on collision or partialcollision. Accordingly, it is possible to effectively protect passengersfrom an impact of collision.

Further, a state of deformation of a frame is controlled by operatingactuators according to an intensity and direction of an external force.Therefore, various strength characteristics such as a breakingcharacteristic and vibration characteristic can be arbitrarily changed.Due to the foregoing, for example, the frame of a car body can beappropriately deformed in collision, so that passengers can be protectedmore positively. Further, when the vibration characteristic is changed,it becomes possible to reduce vibration and noise. Furthermore, whenrigidity of the frame is increased, stability can be enhanced inrunning. Furthermore, various strength characteristics do not rely onthe shape of the frame. Therefore, the degree of freedom of designingthe frame can be advantageously increased.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form can be changed in the details ofconstruction and in the combination and arrangement of parts withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:
 1. A control device for controlling rigidity of acar body comprising: adjustment means for increasing rigidity of a rightside frame and a left side frame extending in a longitudinal directionof the car, said adjustment means being attached to the side frames;collision detection means for detecting a form of collision of the car;and control means for controlling an operation of said adjustment meansaccording to the form of the collision judged by an output of saidcollision detection means.
 2. A control device for controlling rigidityof a car body according to claim 1, wherein said adjustment meanscomprises a solid element actuator to generate a force in a direction ofone of restricting deformation of the side frame and facilitatingdeformation of the side frame.
 3. A control device for controllingrigidity of a car body according to claim 1, wherein said adjustmentmeans comprises a reinforcement member capable of being displacedbetween a first position at which rigidity of the side frame is enhancedand a second position at which no influence is given to rigidity of theside frame.
 4. The control device of claim 1, wherein said adjustingmeans comprises a piezoelectric actuator.
 5. The control device of claim4, wherein each of said right and left side frames includes a curvedportion and wherein said adjusting means is located along an insidesurface of said curved portion.
 6. The control device of claim 1,wherein each of said side frames has an opening therein and wherein saidadjusting means comprises an actuator disposed within said opening, saidactuator including a magentostriction element panel and a coil forgenerating a magnetic field so as to generate a force in themagentostriction element panel to suppress deformation of each of saidside frames.
 7. The control device of claim 1, wherein said adjustingmeans comprises a reinforcing plate disposed inside a channel of each ofsaid side frames, said reinforcing plate being movable from a firstposition in which it engages an abutment in each said side frames and asecond position in which it is displaced from said abutment.
 8. Thecontrol device of claim 1, wherein each of said right and left sideframes includes a curved portion and wherein said adjusting means islocated along said curved portion.